Magnetic assembly for electric timepiece



Dec. 5, 1961 F. KOEHLER ETAL MAGNETIC ASSEMBLY FOR ELECTRIC TIMEPIECEFiled June 20, 1958 FIG. 6

3o INVENTORS FRED KOEHLER DONALD A. BLY

ATTORNEYS United States Patent 3,012,173 MAGNETIC ASSEMBLY FOR ELECTRICTIMEPIECE Fred Koehler and Donald A. Bly, Lancaster, Pa., assignors toHamilton Watch Company, Lancaster, Pa., a corporation of PennsylvaniaFiled June 20, 1958, Ser. No. 743,370

8 Claims. (Cl. 317-458) This invention relates to an electric clock andmore particularly to that part of the clock which furnishes the motivepower for operating the oscillating balance wheel.

The electromagnetic assemblies of certain types of electric clockscontain U-shaped cores with in-turned core legs and with coils mountedon the legs. In the assembly of this unit it is a customary practice towind the coils upon a core after the core is fully assembled, thein-turned ends of the core extending beyond the ends of the coils toform the pole pieces which are used to attract an armature or the like.This construction makes the winding of the coils on the core a difiicultoperation and with certain shapes of cores it is almost impossible towind the coils without the cost being prohibitive.

It is accordingly a primary object of this invention to provide alaminated or multi-piece core which may be assembled after the coil hasbeen wound and which will provide practically the same magnetictransference as a solid core. I

It is a further object of the present invention to provide a multi-piececore substantially U-shaped with the legs diverging to lessen theleakage across the legs and to concentrate the flow of flux through polepieces which are attached to the core and extend substantially at rightangles to the legs of the Ushaped core.

It is another object of the invention to utilize the ends of a laminatedcore of the coil to substantially cover the ends of the armature so thatthe magnetic field is intensified and substantially restricted.

It is another object of the present invention to make the core of sixindividual pieces which are fabricated in three pairs to provideinterchangeability and economy in manufacturing.

It is a still further object of the present invention to provide a smalltolerance between the individual parts making up the core so that duringthe mounting operation of the coil in the watch the pieces may beslightly spaced to provide for any inaccuracies in the hole placement.

These and further objects and advantages of the invention will becomemore apparent on reference to the following specification and claims andappended drawings in which:

FIGURE 1 is a top plan view of a core and coil assembly according to theinvention with the coils shown in cross section;

FIGURE 2 is an end view of the assembly of FIG- URE 1;

FIGURE 3 is a side elevation of the assembly of FIGURE 1 with the coilshown in cross section;

FIGURE 4 is a plan view of one of the core pieces;

FIGURE 5 is a plan view of another of the core pieces; and

FIGURE 6 is a plan view of the third core piece.

Referring particularly to FIGURES 4, 5 and 6, the parts which make upthe laminated core are made in three identical pairs. One of these corepairs is illustrated in FIGURE 4, the second is illustrated in FIG- URE5, and the third is illustrated in FIGURE 6.

The substantially U-shaped part illustrated in FIG- URE 4 is formed witha base portion 12, a short leg 14 and a long leg 16, the legs and basebeing of one piece of flat sheet material which is preferably stamped.The

3,012,173 Patented Dec. 5, 1961 base 12 is formed with a central hole 18used in positioning the completed coil in the time piece.

The part illustrated in FIGURE 5 is substantially V-shaped with arounded apex portion 20, a long leg 24, and a pole piece 26. This isreferred to as the large V-member. The apex portion 20 of the V-memberis apertured at 22 and this aperture is used to position the completedassembly in the watch or clock.

The part shown in FIGURE 6 is very similar to the one shown in FIGURE 5and is referred to as the small V-rnember. This member has a roundedapex portion 28 formed with a central hole 30, a pole piece 32 and ashort leg 34.

Referring particularly to FIGURE 1, when the core is assembled the baseportions of the two U-shaped members 12 are superimposed so that theupper long leg 16 of one piece is superimposed over the upper short leg14 of the other piece, and conversely, the lower short leg of the firstpiece is above the lower longer leg of the second piece. The V-mem-bersshown in FIGURES 5 and 6 are mounted in this assembly with theirrespective legs 24 and 34 abutting the ends of the legs of the U- shapedmembers. Thus referring to FIGURE 1, the up per leg of the assembly inthe drawing has a long leg 24 of the large V-member shown in FIGURE 5abutting the short leg 14 of the bottom U-shaped member, and has a shortleg 34 of the small V-member shown in FIG- URE 6 abutting the long leg16 of the U-shaped member. The lower leg of the assembly is converselyassembled.

In order that the tolerances between the holes 18, 30 and 22 need not beso rigid as to require unduly accurate dimensioning, it is desirable toprovide slight air gaps at the abutments 36 and 38 of the legs of theU-shaped members and the legs of the V-members shown in FIGURES 5 and 6.The overlapping of the legs of the U-shaped members and the legs of theV-members provides good magnetic transference throughout the laminatedcore and also tends to minimize stray fields which might be formed wherethere was an air gap.

The coils 40 are identical and are prewound and then separately slippedonto the legs of the U'shaped members. The legs of the V-members arethen inserted into position.

This particular method of laminating the core structure makes for easeof assembling and ease in manufacturing.

Referring particularly to FIGURE 2, it will be seen that the pole pieces26 and 32 of the U-members are identical and are bent at 42 and 44respectively to provide a gap 46 through which an armature may pass. The

gap 46 tends to intensify and restrict the magnetic field thus supplyinga maximum of magnetic flux at the point at which it is required whilepreventing or minimizing the eifect of a large magnetic field on theother parts of the timepiece such as the hairspring, the gear trainwheels and the pivot staffs.

The invention may be embodied in other specific form without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not re trictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to States Letters Patent is:

1. An electromagnet for an electric timepiece comprising a pair ofidentical substantially U-shaped core pieces each having a base and along and a short leg; said core pieces being arranged in overlappingrelationship so that be secured by United their bases coincide and thelong leg of each piece overlies the short leg of the other piece; twopairs of laminated pole pieces, each pair comprising two laminae eachhaving-.angularly arranged .first and second portions; the first portionof the firstlaminabeing longer than the first portion of the secondlamina; each pair of pole pieces being associated with one pair ofoverlapping legs of .said .core pieces so that the first portion of thefirst lamina of said pair of pole pieces-overlaps thelongleg of saidcore pieces; the end \of .said long leg being adjacent the end of thefirst portion of the second lamina of said pair of ,pole pieces; :and .apair of coils each disposed about the overlapping legs and firstportions of said associated core pieces .and pole pieces.

2. An electromagnet as defined in claim 1 wherein said pole pieces aregenerally U-shaped; the second portions .of .said pole pieces beingformed .at substantially right angles to their respective firstportions.

3. An .electromagnet as defined in claim 1 wherein the second portionsof the laminae in each pair of pole pieces are spaced from one anotherto form a bifurcation; the open .ends of the two bifurcations facing onean-. other :and the two pairs of .pole pieces being arranged so .as topermit an armature to rotate with its endspassing within the .twobifurcations.

4. .An electromagnet as defined in claim 1 wherein said long and short,legs of said U-shaped core pieces diverge from the bases of saidpieces.

v5. electromagnet for an electric timepiece comprising a ,pair of coils;a pair of identical substantially Uashaped core pieces each having abase and a long and ashortleg; .the base and the legs of each piecebeing arranged in overlapping relationship with the respective base andlegs .of the other .piece so that the short leg of one .piece overliesthe long leg of the other piece; and

-a laminated pole piece associated with each mating pair .of legs; each,polexpiece having a first portion formed of two laminae .of differentlengths to conform to its associated pair of mating long and short legsof said core pieces; .the long .legs of said associated core and pole,pieces overlapping one :ano:ther,;-eac'h pole piece .having a saidpiece and extending in the direction of the second portion of the otherpole piece; said coils being disposed about the overlapping legs of saidcore and pole pieces.

6. An electromagnet for an electric timepiece comprising a pair ofsubstantially U-shaped core pieces each having a base and two legs; thebase and legs of one of said pieces overlying the respective base andlegs of the other of said pieces; the legs of each core piece beingconstructed relative to one another and to the legs of :the other corepiece so that one of the legs on each-side of the U is longer than theother leg on the same side. of said U; two pairs of laminated polepieces, each pair comprising :two laminae each having angularly arranged.secondportion formedtat an angle to the first portion of first andsecond portions; the first portion of the first lamina, being longerthan the first portion of the second lamina; each .pair of polepiece'sbeing associated with one pair ofoverlapping legs of said core pieces sothat the first .portion of the first lamina of said pair of ,pole,pieces'overlaps the long leg of said associated pair of legs; .the endof said long leg being adjacent the end of first :portion .of the secondlamina of said associated pair of pole pieces; the second portions ofthe 'laminae in each .pair of .pole pieces being spaced from one another"to form a bifurcation; the open ends of the two bifurcations facing oneanother and the two pairs of pole pieces be ing arrangedso as to permitan armature to rotate with its ends passing within thetwo bifurcations;and a pair .of coils each disposedtabout the mated legs andfirstportions of said associated core pieces andpole pieces.

7. .An .electromagnet according to claim 5 wherein the ends of saidsecond portions of said pole pieces are bifurcated to permit an armatureto reciprocate between the furcations of each such .portion.

' 8. An electro-magnet according to claim '5 wherein said .long andshort legs of said U-s'haped'core pieces diverge from said base.

References Cited'in the file of this patent UNITED STATES PATENTS495,562 Perret 1 8, 1893 1,711,657 Sanders ...1.'M-ay 7, 1-9 29

